Dowlingoceras sp. A

Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, European Journal of Taxonomy 978, pp. 1-169 : 72

Dowlingoceras sp. A

Fig. 27B–C, E

Material examined

ESTONIA • Vohilaid Island, Vohilaid shore (E); Adila Formation , Pirgu Regional Stage, GIT 878-249 .

Description

The specimen is an internal mold of a mature body chamber with a conch height and width at its base of 44 mm and 38 mm, respectively (CHI = 1.2). At the peristome, the height and width are 40 mm and 32 mm, respectively. The body chamber is 36 mm long and in lateral view has slightly convex margins. The conch cross section is elliptical. At a distance of ca 10 mm from the peristome, a ca 10 mm wide and 1.5 mm deep constriction forms an amphora-like aperture. The peristome is directly transverse with a wide, inconspicuous hyponomic sinus on the prosiphuncular side. Traces of a septal foramen close to the conch margin are preserved.

Remarks

The specimen is assigned to Dowlingoceras based on shape of the mature body chamber. Its size and rounded elliptical cross section can be compared with D. torni , while the gibbous shape and terminal constriction can be compared with D. kallholnense . Based on this single incomplete specimen, erection of a new species is impossible.

Figures

Fig. 27 (next page). Breviconic cephalopods from the Vormsi–Pirgu regional stages, Estonia. A. Dowlingoceras kallholnense Frye, 1987, specimen GIT 878-247, from Hosholm shore (tower),Vormsi Island, Pirgu Regional Stage, lateral view. B–C, E. Dowlingoceras sp., specimen GIT 878-249, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage. B. Lateral view. C. View of antisiphuncular side. D. Danoceras sp. A., specimen GIT 878-269, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view.E. Adoral view. F. Rizosceras teres sp. nov., holotype TUG 1745-188, from Saaremõisa (Lyckholm), Vormsi Regional Stage, lateral view. G–H. Kallholnoceras sp. G. GIT 878- 323, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. H. Specimen GIT 878-233, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage, lateral view. I. Dowlingoceras tornense sp. nov., holotype GIT 840-254, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. J. Dowlingoceras sp. B, specimen GIT 47-866, from Vohilaid shore (E), Vohilaid Island, Pirgu Regional Stage, lateral view. K. Diestoceras sp., specimen GIT 878-252, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. L. Diestoceras stensioei (Troedsson, 1926), specimen GIT 426-987, from Piirsalu quarry, Pirgu Regional Stage. M. Diestoceratidae gen. et sp. indet., specimen TUG 1745-192, from Salu, Pirgu Regional Stage, view from antisiphuncular (?) side. N. Diestoceras stensioei (Troedsson, 1926), specimen GIT 840-264, from Hosholm shore (tower), Vormsi Island, Pirgu Regional Stage, lateral view. Scale bar = 10 mm, same scale in all figures.